Light

No doubt we've all noticed the lengthening days as the winter winds down and we make our way towards the summer solstice (the longest day of the year). As we look at the natural world around us, light, in its most basic form, is very important to the plants and animals adapted to the area.

For the local plants, light is one of the most important factors in determining which plants will occur in a given area. For instance, when some natural disaster, like fire, opens up an area, you will find a rapid invasion of sun loving plants like fireweed. This will be accompanied with the growth of trees like the trembling aspen and lodgepole pine--both very well adapted to living in direct sunlight. In fact they are so well adapted to sunlight that they cannot live in dense shade.

There are plants adapted to living within the domain of shade, and they will creep in below the sun loving pine and aspen. Slowly, as time passes, and the pioneers slowly expire, they will become the dominant species. The reason for this lies in the fact that the pine and aspen will be unable to grow beneath their own, or any other trees, shade. Spruce trees, on the other hand, are well adapted to living in the shade and will slowly take over.

For animals, light plays an equally important factor in survival. It affects them directly in the ways in which they detect both food and predators. There are very few animal groups without at least some rudimentary method of sensing light--and this even includes the most basic of one celled animals. Some animals have developed forms of camouflage that enable them to fool other animals sense of sight. This may enable them to capture or avoid being captured.

Sensitivity to light varies with different animal groups with some being better adapted to higher or lower levels. For instance birds like hawks normally hunt during the daytime while their avian cousins, owls, are much better adapted to hunting in lower light levels.

There are very few forms of life that have adapted to living within the total darkness found in caves. Among the plant kingdom, they are generally either bacteria or fungi and survive by living on organic material brought in from the outside. Most of the other residents either have to leave the cave to find food or, like the fungi, survive on what has already been brought in by other animals.

Bats are fascinating in their adaptations to darkness. They use a form of sonar that allows them to effectively see in total darkness. They send out high pitched signals which are reflected from solid objects providing an echo which only the bat can hear. By reacting to these echoes they can fly in areas where there is no light source.